As a growing number of users switch to mobile phones and tablets as their primary method of accessing the Internet, ad-supported Web services are turning to mobile screens. About 55 per cent of Twitter's over 100 million monthly active users access its service over a mobile phone.

Initially, only a small number of users will see promoted tweets on their mobile phones, Twitter said on it blogpost.

Since 2010, Twitter's in-house sales staff has sold "promoted tweets" to large businesses on a case-by-case basis, but this month, the company launched a similar service to allow small businesses to buy and place ads on the online messaging platform.

The company's service lets people send 140-character messages, or tweets, to groups of followers. Twitter has more than 100 million active users and a valuation topping $8 billion, even though it does not yet have a significant money-making model.